Present the printer list from preferences for Chrome OS.

chrome/browser/ui/webui/print_preview/printer_backend_proxy_chromeos.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/ui/webui/print_preview/printer_backend_proxy.h"
+
+#include <memory>
+#include <vector>
+
+#include "base/values.h"
+#include "chrome/browser/chromeos/printing/printer_pref_manager.h"
+#include "chrome/browser/chromeos/printing/printer_pref_manager_factory.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chromeos/printing/printer_configuration.h"
+#include "content/public/browser/browser_thread.h"
+#include "printing/backend/print_backend.h"
+
+namespace printing {
+
+std::string GetDefaultPrinterOnBlockingPoolThread() {
+  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+  return "";

[Lei Zhang, 2016/10/28 21:55:51]

Is this intentional or will it be filled in with some other value in a follow-up
CL?

[skau, 2016/11/02 22:00:03]

We don't have default printers in Chrome OS right now.  It will be added in the
near future.

[Lei Zhang, 2016/11/02 22:40:59]

If there is a bug # for that, please include it for reference.

[skau, 2016/11/02 23:38:16]

Done.

+}
+
+PrinterList EnumeratePrintersOnBlockingPoolThread(Profile* profile) {
+  DCHECK(content::BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+
+  chromeos::PrinterPrefManager* prefs =
+      chromeos::PrinterPrefManagerFactory::GetForBrowserContext(profile);
+  std::vector<std::unique_ptr<chromeos::Printer>> printers =
+      prefs->GetPrinters();
+  PrinterList printer_list;
+  for (const std::unique_ptr<chromeos::Printer>& printer : printers) {
+    PrinterBasicInfo basic_info;
+    basic_info.printer_id = printer->id();
+    basic_info.printer_name = printer->display_name();
+    basic_info.printer_description = printer->display_name();
+    printer_list.push_back(std::move(basic_info));
+  }
+
+  return printer_list;
+}
+
+}  // namespace printing